Network Working Group X. Xu
Internet Draft D. Zhang
Category: Standard Track L.Xia
Huawei
Expires: December 2016 October 31, 2016
Encapsulating IPsec ESP in UDP for Load-balancing
draft-xu-ipsecme-esp-in-udp-lb-00
Abstract
IPsec Virtual Private Network (VPN) is widely used by enterprises to
interconnect their geographical dispersed branch office locations
across IP Wide Area Network (WAN). To fully utilize the bandwidth
available in IP WAN, load balancing of traffic between different
IPsec VPN sites over Equal Cost Multi-Path (ECMP) and/or Link
Aggregation Group (LAG) within IP WAN is attractive to those
enterprises deploying IPsec VPN solutions. This document defines a
method to encapsulate IPsec Encapsulating Security Payload (ESP)
packets inside UDP packets for improving load-balancing of IPsec
tunneled traffic. In addition, this encapsulation is also applicable
to some special multi-tenant data center network environment where
the overlay tunnels need to be secured.
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This Internet-Draft will expire on December 31, 2016.
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Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [RFC2119].
Table of Contents
1. Introduction ................................................ 3
2. Terminology ................................................. 4
3. Encapsulating ESP in UDP .................................... 4
4. Encapsulation and Decapsulation Procedures .................. 5
5. Congestion Considerations ................................... 5
6. Security Considerations ..................................... 5
7. IANA Considerations ......................................... 6
8. Acknowledgements ............................................ 6
9. References .................................................. 6
9.1. Normative References ................................... 6
9.2. Informative References ................................. 6
Authors' Addresses ............................................. 7
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1. Introduction
IPsec Virtual Private Network (VPN) is widely used by enterprises to
interconnect their geographical dispersed branch office locations
across IP Wide Area Network (WAN). To fully utilize the bandwidth
available in IP WAN, load balancing of traffic between different
IPsec VPN sites over Equal Cost Multi-Path (ECMP) and/or Link
Aggregation Group (LAG) within IP WAN is much attractive to those
enterprises that deploy IPsec VPN solutions. Since most existing
core routers within IP WAN can already support balancing IP traffic
flows based on the hash of the five-tuple of UDP packets, by
encapsulating IPsec Encapsulating Security Payload (ESP) packets
inside UDP packets with the UDP source port being used as an entropy
field, it will enable existing core routers to perform efficient
load-balancing of the IPsec tunneled traffic without requiring any
change to them. Therefore, this specification defines a method of
encapsulating IPsec ESP packets inside UDP packets for improving
load-balancing of IPsec tunneled traffic. This is similar to why
LISP [RFC6830], MPLS-in-UDP [RFC7510] and VXLAN [RFC7348] use UDP
encapsulation.
In addition, this encapsulation is also applicable to some special
multi-tenant data center network environment where the overlay
tunnels need to be secured while the UDP-based ECMP capability is
desired as well (see [draft-ietf-nvo3-use-case]).
Encapsulating ESP in UDP, as defined in this document, can be used
in both IPv4 and IPv6 scenarios. IPv6 flow label has been proposed
as an entropy field for load balancing in IPv6 network environment
[RFC6438]. However, as stated in [RFC6936], the end-to-end use of
flow labels for load balancing is a long-term solution and therefore
the use of load balancing using the transport header fields would
continue until any widespread deployment is finally achieved. As
such, IP-in-UDP encapsulation would still have a practical
application value in the IPv6 networks during this transition
timeframe.
Note that the difference between the ESP-in-UDP encapsulation as
proposed in this document and the ESP-in-UDP encapsulation as
described in [RFC3948] is that the former uses the UDP tunnel for
load-balancing improvement purpose and therefore the source port is
used as an entropy field while the latter uses the UDP tunnel for
NAT traverse purpose and therefore the source port is set to a
constant value (i.e., 4500). In addition, the document only
discusses about the tunnel mode ESP encapsulation.
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2. Terminology
This memo makes use of the terms defined in [RFC2401] and [RFC2406].
3. Encapsulating ESP in UDP
ESP-in-UDP encapsulation format is shown as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port = entropy | Dest Port = ESP |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ ESP Packet ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Source Port of UDP
This field contains a 16-bit entropy value that is
generated by the encapsulator to uniquely identify a
flow. What constitutes a flow is locally determined by
the encapsulator and therefore is outside the scope of
this document. What algorithm is actually used by the
encapsulator to generate an entropy value is outside the
scope of this document. In case the tunnel does not need
entropy, this field of all packets belonging to a given
flow SHOULD be set to a randomly selected constant value
so as to avoid packet reordering.
To ensure that the source port number is always in the
range 49152 to 65535 (Note that those ports less than
49152 are reserved by IANA to identify specific
applications/protocols) which may be required in some
cases, instead of calculating a 16-bit hash, the
encapsulator SHOULD calculate a 14-bit hash and use
those 14 bits as the least significant bits of the
source port field while the most significant two bits
SHOULD be set to binary 11. That still conveys 14 bits
of entropy information which would be enough as well in
practice.
Destination Port of UDP
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This field is set to a value (TBD) indicating the
encapsulated payload in the UDP header is an ESP packet.
UDP Length
The usage of this field is in accordance with the
current UDP specification [RFC768].
UDP Checksum
For IPv4 UDP encapsulation, this field is RECOMMENDED to
be set to zero for performance or implementation reasons
because the IPv4 header includes a checksum and use of
the UDP checksum is optional with IPv4. For IPv6 UDP
encapsulation, the IPv6 header does not include a
checksum, so this field MUST contain a UDP checksum that
MUST be used as specified in [RFC0768] and [RFC2460]
unless one of the exceptions that allows use of UDP
zero-checksum mode (as specified in [RFC6935]) applies.
4. Encapsulation and Decapsulation Procedures
This ESP-in-UDP encapsulation causes ESP [RFC2406] packets to be
forwarded across IP WAN via "UDP tunnels". When performing ESP-in-
UDP encapsulation by an IPsec VPN gateway, ordinary ESP
encapsulation procedure is performed and then a formatted UDP header
is inserted between ESP header and IP header. The Source Port field
of the UDP header is filled with an entropy value which is generated
by the IPsec VPN gateway.
Upon receiving these UDP encapsulated packets, remote IPsec VPN
gateway MUST decapsulate these packets by removing the UDP header
and then perform ordinary ESP decapsulation procedure consequently.
5. Congestion Considerations
TBD
6. Security Considerations
TBD.
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7. IANA Considerations
A new UDP destination port number which indicates the encapsulated
payload following the UDP header is an ESP packet needs to be
assigned by IANA.
8. Acknowledgements
Thanks to.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
9.2. Informative References
[RFC768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
[RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC 2401, November 1998.
[RFC2406] Kent, S. and R. Atkinson, "IP Encapsulating Security
Payload (ESP)", RFC 2406, November 1998.
[RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "UDP
Checksums for Tunneled Packets", RFC6935, Feburary 2013.
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
Stenberg, "UDP Encapsulation of IPsec Packets", RFC 3948,
January 2005.
[RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement
for the use of IPv6 UDP Datagrams with Zero Checksums",
RFC6936, Feburary 2013.
[RFC7510] Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black,
"Encapsulating MPLS in UDP", RFC 7510,
DOI 10.17487/RFC7510, April 2015,
<http://www.rfc-editor.org/info/rfc7510>.
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Authors' Addresses
Xiaohu Xu
Huawei Technologies,
Beijing, China
Phone: +86-10-60610041
Email: xuxiaohu@huawei.com
Dacheng Zhang
Huawei Technologies,
Beijing, China
Phone: +86-13621142434
Email: dacheng.zhang@huawei.com
Liang Xia
Huawei Technologies,
Email: frank.xialiang@huawei.com
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